From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTPS id DBC473858C27 for ; Wed, 17 Nov 2021 03:24:47 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DBC473858C27 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-563-HDYLkLylM_mZ_2SxF4p6rw-1; Tue, 16 Nov 2021 22:24:44 -0500 X-MC-Unique: HDYLkLylM_mZ_2SxF4p6rw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DB170E75A; Wed, 17 Nov 2021 03:24:42 +0000 (UTC) Received: from localhost.localdomain.com (unknown [10.22.17.164]) by smtp.corp.redhat.com (Postfix) with ESMTP id D13E619D9B; Wed, 17 Nov 2021 03:24:41 +0000 (UTC) From: Aaron Merey To: simon.marchi@polymtl.ca Cc: gdb-patches@sourceware.org, tom@tromey.com, lsix@lancelotsix.com Subject: Re: [PATCH 2/3] gdb: Add soname to build-id mapping for corefiles Date: Tue, 16 Nov 2021 22:24:41 -0500 Message-Id: <20211117032441.719270-1-amerey@redhat.com> In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-13.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 17 Nov 2021 03:24:50 -0000 Hi Simon, On Sat, Nov 13, 2021 at 9:37 PM Simon Marchi wrote: > > +     filename_map[filename] = build_id = vma_map_it->second; > > Please avoid doing two assignments in one statement. Fixed. > > +gdb::optional > > +gdb_bfd_read_elf_soname (struct bfd *bfd) > > +{ > > +  gdb_assert (bfd != nullptr); > > + > > +  gdb_bfd_ref_ptr abfd = gdb_bfd_open (bfd->filename, gnutarget); > > Can you explain why we are opening bfd->filename?  Doesn't "abfd" > represent the exact same thing than "bfd"?  So why can't we use "bfd" > directly to look up the soname? bfd->flags does not contain the correct value. This causes the check for ET_DYN to fail even for shared libraries. Also bfd->build_id always seems to be NULL. Opening "abfd" with gdb_bfd_open and passing it to bfd_check_format populates flags and build_id with the correct values. Passing "bfd" to bfd_check_format still does not populate these fields with the correct values. It looks like this happens because the format of "abfd" is initially set to bfd_unknown. In this case bfd_check_format rereads the file and updates some fields with the correct values, including flags and build_id. Since format of "bfd" is instead bfd_object, bfd_check_format returns early and skips updating any fields. Thanks, Aaron >From 275e69ce65aa3d5ee3b017175c73f8536a1fb559 Mon Sep 17 00:00:00 2001 From: Aaron Merey Date: Tue, 16 Nov 2021 17:33:52 -0500 Subject: [PATCH 2/3] gdb: Add soname to build-id mapping for core files Since commit aa2d5a422 gdb has been able to read executable and shared library build-ids within core files. Expand this functionality so that each program_space maintains a map of soname to build-id for each shared library referenced in the program_space's core file. This feature may be used to verify that gdb has found the correct shared libraries for core files and to facilitate downloading shared libaries via debuginfod. --- gdb/corelow.c | 11 +++++++++++ gdb/linux-tdep.c | 38 +++++++++++++++++++++++++++++++++++++- gdb/progspace.c | 32 ++++++++++++++++++++++++++++++++ gdb/progspace.h | 18 ++++++++++++++++++ gdb/solib.c | 35 +++++++++++++++++++++++++++++++++++ gdb/solib.h | 5 +++++ 6 files changed, 138 insertions(+), 1 deletion(-) diff --git a/gdb/corelow.c b/gdb/corelow.c index 10942e6af01..d1256a9e99b 100644 --- a/gdb/corelow.c +++ b/gdb/corelow.c @@ -282,6 +282,16 @@ core_target::build_file_mappings () /* Set target_section fields. */ m_core_file_mappings.emplace_back (start, end, sec); + + /* If this is a bfd of a shared library, record its soname + and build id. */ + if (build_id != nullptr) + { + gdb::optional soname = gdb_bfd_read_elf_soname (bfd); + if (soname) + current_program_space->set_cbfd_soname_build_id + (std::move (*soname), build_id); + } }); normalize_mem_ranges (&m_core_unavailable_mappings); @@ -305,6 +315,7 @@ core_target::close () comments in clear_solib in solib.c. */ clear_solib (); + current_program_space->clear_cbfd_soname_build_ids (); current_program_space->cbfd.reset (nullptr); } diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c index e2cff83086a..7325ba67208 100644 --- a/gdb/linux-tdep.c +++ b/gdb/linux-tdep.c @@ -44,6 +44,7 @@ #include "solib-svr4.h" #include +#include /* This enum represents the values that the user can choose when informing the Linux kernel about which memory mappings will be @@ -1170,6 +1171,23 @@ linux_read_core_file_mappings if (f != descend) warning (_("malformed note - filename area is too big")); + const bfd_build_id *orig_build_id = cbfd->build_id; + std::unordered_map vma_map; + std::unordered_map filename_map; + + /* Search for solib build-ids in the core file. Each time one is found, + map the start vma of the corresponding elf header to the build-id. */ + for (bfd_section *sec = cbfd->sections; sec != nullptr; sec = sec->next) + { + cbfd->build_id = nullptr; + + if (sec->flags & SEC_LOAD + && get_elf_backend_data (cbfd)->elf_backend_core_find_build_id + (cbfd, (bfd_vma) sec->filepos)) + vma_map[sec->vma] = cbfd->build_id; + } + + cbfd->build_id = orig_build_id; pre_loop_cb (count); for (int i = 0; i < count; i++) @@ -1183,8 +1201,26 @@ linux_read_core_file_mappings descdata += addr_size; char * filename = filenames; filenames += strlen ((char *) filenames) + 1; + const bfd_build_id *build_id = nullptr; + auto vma_map_it = vma_map.find (start); + + /* Map filename to the build-id associated with this start vma, + if such a build-id was found. Otherwise use the build-id + already associated with this filename if it exists. */ + if (vma_map_it != vma_map.end ()) + { + build_id = vma_map_it->second; + filename_map[filename] = build_id; + } + else + { + auto filename_map_it = filename_map.find (filename); + + if (filename_map_it != filename_map.end ()) + build_id = filename_map_it->second; + } - loop_cb (i, start, end, file_ofs, filename, nullptr); + loop_cb (i, start, end, file_ofs, filename, build_id); } } diff --git a/gdb/progspace.c b/gdb/progspace.c index 7080bf8ee27..680c5ba8f0a 100644 --- a/gdb/progspace.c +++ b/gdb/progspace.c @@ -18,6 +18,7 @@ along with this program. If not, see . */ #include "defs.h" +#include "build-id.h" #include "gdbcmd.h" #include "objfiles.h" #include "arch-utils.h" @@ -358,6 +359,37 @@ print_program_space (struct ui_out *uiout, int requested) } } +/* See progspace.h. */ + +void +program_space::set_cbfd_soname_build_id (std::string soname, + const bfd_build_id *build_id) +{ + m_cbfd_soname_to_build_id[std::move (soname)] = build_id_to_string (build_id); +} + +/* See progspace.h. */ + +const char * +program_space::get_cbfd_soname_build_id (const char *soname) +{ + gdb_assert (soname); + + auto it = m_cbfd_soname_to_build_id.find (basename (soname)); + if (it == m_cbfd_soname_to_build_id.end ()) + return nullptr; + + return it->second.c_str (); +} + +/* See progspace.h. */ + +void +program_space::clear_cbfd_soname_build_ids () +{ + m_cbfd_soname_to_build_id.clear (); +} + /* Boolean test for an already-known program space id. */ static int diff --git a/gdb/progspace.h b/gdb/progspace.h index fb348ca7539..01af5a387e3 100644 --- a/gdb/progspace.h +++ b/gdb/progspace.h @@ -30,6 +30,7 @@ #include "gdbsupport/safe-iterator.h" #include #include +#include struct target_ops; struct bfd; @@ -324,6 +325,19 @@ struct program_space /* Binary file diddling handle for the core file. */ gdb_bfd_ref_ptr cbfd; + /* Associate a core file SONAME with BUILD_ID so that it can be retrieved + with get_cbfd_soname_build_id. */ + void set_cbfd_soname_build_id (std::string soname, + const bfd_build_id *build_id); + + /* If a core file SONAME had a build-id associated with it by a previous + call to set_cbfd_soname_build_id then return the build-id as a + NULL-terminated hex string. */ + const char *get_cbfd_soname_build_id (const char *soname); + + /* Clear all core file soname to build-id mappings. */ + void clear_cbfd_soname_build_ids (); + /* The address space attached to this program space. More than one program space may be bound to the same address space. In the traditional unix-like debugging scenario, this will usually @@ -378,6 +392,10 @@ struct program_space /* The set of target sections matching the sections mapped into this program space. Managed by both exec_ops and solib.c. */ target_section_table m_target_sections; + + /* Mapping of a core file's shared library sonames to their + respective build-ids. */ + std::unordered_map m_cbfd_soname_to_build_id; }; /* An address space. It is used for comparing if diff --git a/gdb/solib.c b/gdb/solib.c index 3947c2d1d2e..c0beea19d7b 100644 --- a/gdb/solib.c +++ b/gdb/solib.c @@ -23,6 +23,7 @@ #include #include "symtab.h" #include "bfd.h" +#include "build-id.h" #include "symfile.h" #include "objfiles.h" #include "gdbcore.h" @@ -1586,6 +1587,40 @@ gdb_bfd_scan_elf_dyntag (const int desired_dyntag, bfd *abfd, CORE_ADDR *ptr, return 0; } +/* See solib.h. */ + +gdb::optional +gdb_bfd_read_elf_soname (struct bfd *bfd) +{ + gdb_assert (bfd != nullptr); + + gdb_bfd_ref_ptr abfd = gdb_bfd_open (bfd->filename, gnutarget); + + if (abfd == nullptr) + return {}; + + /* Check that bfd is an ET_DYN ELF file. */ + bfd_check_format (abfd.get (), bfd_object); + if (!(bfd_get_file_flags (abfd.get ()) & DYNAMIC)) + return {}; + + /* Determine soname of shared library. If found map soname to build-id. */ + CORE_ADDR idx; + if (!gdb_bfd_scan_elf_dyntag (DT_SONAME, abfd.get (), &idx, nullptr)) + return {}; + + struct bfd_section *dynstr = bfd_get_section_by_name (abfd.get (), ".dynstr"); + if (dynstr == nullptr || bfd_section_size (dynstr) <= idx) + return {}; + + /* Read the soname from the string table. */ + gdb::byte_vector dynstr_buf; + if (!gdb_bfd_get_full_section_contents (abfd.get (), dynstr, &dynstr_buf)) + return {}; + + return std::string ((const char *)dynstr_buf.data () + idx); +} + /* Lookup the value for a specific symbol from symbol table. Look up symbol from ABFD. MATCH_SYM is a callback function to determine whether to pick up a symbol. DATA is the input of this callback function. Return NULL diff --git a/gdb/solib.h b/gdb/solib.h index c50f74e06bf..51cc047463f 100644 --- a/gdb/solib.h +++ b/gdb/solib.h @@ -118,6 +118,11 @@ extern CORE_ADDR gdb_bfd_lookup_symbol_from_symtab (bfd *abfd, extern int gdb_bfd_scan_elf_dyntag (const int desired_dyntag, bfd *abfd, CORE_ADDR *ptr, CORE_ADDR *ptr_addr); +/* If BFD is an ELF shared object then attempt to return the string + referred to by its DT_SONAME tag. */ + +extern gdb::optional gdb_bfd_read_elf_soname (struct bfd *bfd); + /* Enable or disable optional solib event breakpoints as appropriate. */ extern void update_solib_breakpoints (void); -- 2.31.1